The Kakuma refugee camp is a truly terrible place. Somewhere in the region of eighty or ninety thousand people are crammed into a small space without adequate food, water, or shelter. Isolated in the middle of a dry, windy desert, Kakuma is surrounded by high barbed-wire fences that make it look for all the world like a prison.
To make matters worse, local people deeply resent the presence of the camp and the refugees who live there. They often sneak into the camp and steal from the refugees. Fights regularly break out in which some people are actually killed.
Most of the refugees in Kakuma are young men and orphaned boys. There are some families there who've managed to escape the ongoing conflict together, but they're very much in a minority. This is largely due to the fact that many families have been broken up by the war and so have not been able to travel together.
The presence of a large number of young men at the camp indicates that perhaps there have been desertions from the respective armies or that maybe young men are running away in order to avoid being forcibly conscripted to fight.
In any case, Kakuma is such an unmitigated misery that Salva decides to leave the camp and seek a better one elsewhere, far to the south and west.